Carmina Gadelica, Volume 1, by Alexander Carmicheal, [1900], at sacred-texts.com

DIARDAOIN, Didaoirn--the day between the fasts--Thursday, was St Columba's Day--Diardaoin Chaluim-chille, St Columba's Thursday--and through him the day of many important events in the economy of the people. It was a lucky day for all enterprises--for warping thread, for beginning a pilgrimage, or any other undertaking. On Thursday eve the mother of a family made a bere, rye, or oaten cake into which she put a small silver coin. The cake was toasted before a fire of rowan, yew, oak, or other sacred wood. On the morning of Thursday the father took a keen-cutting knife and cut the cake into as many sections as there were children in the family, all the sections being equal. All the pieces were then placed in a 'ciosan'--a beehive basket--and each child blindfold drew a piece of cake from the basket in name of the Father, Son, and Spirit. The child who got the coin got the crop of lambs for the year. This was called 'sealbh uan'--lamb luck. Sometimes it was arranged that the person who got the coin got a certain number of the lambs, and the others the rest of the lambs among them. Each child had a separate mark, and there was much emulation as to who had most lambs, the best lambs, and who took best care of the lambs.

Maunday Thursday is called in Uist 'Diardaoin a brochain,' Gruel Thursday, and in Iona 'Diardaoin a brochain mhoir,' Great Gruel Thursday. On this day people in maritime districts p. 163 made offerings of mead, ale, or gruel to the god of the sea. As the day merged from Wednesday to Thursday a man walked to the waist into the sea and poured out whatever offering had been prepared, chanting:--

Those behind the offerer took up the chant and wafted it along the sea-shore on the midnight air, the darkness of night and the rolling of the waves making the scene weird and impressive. In 1860 the writer conversed in Iona with a middle-aged man whose father, when young, had taken part in this ceremony. In Lewis the custom was continued till this century. It shows the tolerant spirit of the Columban Church and the tenacity of popular belief, that such a practice should have been in vogue so recently.

The only exception to the luck of Thursday was when Beltane fell on that day.